An important requirement for long term human space flight is to provide the means necessary to maintain the health and physiological well being of the astronauts to ensure their ability to function both in weightlessness/microgravity and during and after landing.
Since the beginning of human space flight, adjusting to weightlessness/microgravity and readjusting to gravity has been of great concern for both the health and safety of the astronauts. Orthostatic intolerance, or fainting, is a serious concern during return to earth gravity after even short periods of weightlessness, especially for the flight crew responsible for piloting and landing the vehicle.
Among other problems of weightlessness, especially on long flights, are the loss of muscle tissue and bone strength which reduce the astronauts ability to perform essential tasks in a gravity environment.
These problems become compounded the longer the period of weightlessness. Providing simulated gravity using centrifugation has long been of interest as a countermeasure to these effects but remains unresolved to date partly due to the lack of adequate means to properly evaluate its efficacy both in space and on the ground.
In an analogous situation, long term bedrest due to injury or illness or even longterm inactivity such as with aging, can result in physiological changes similar to those found in astronauts during periods of weightlessness/microgravity. As a result, one of the frequently used ground models for studying these effects has been bedrest, especially when a 6.degree. headdown tilt is used.
The use of passive (standing) methods of increasing the gravity stimulus on earth, has been shown to reduce orthostatic intolerance when used during bedrest. Active (treadmill exercise) exposure to G force during the same period of bedrest prevents other debilitating effects including calcium loss (which leads to bone strength loss), when compared with non G force exposure (continuous bedrest with no standing or exercise) for the same subjects, periods of time, and other conditions.
Human powered centrifuges have been in existence at least since the late 1700's. The use of these early devices varied from therapeutic to punishment. Later versions were designed primarily for entertainment or curiosity.
U.S. Pat. No. 5,378,214 to Kreitenberg discloses a self-powered human centrifuge which is described to be capable of simulating gravity and providing an aerobic workout as a countermeasure to the adverse physiological effects of prolonged spaceflight. The device includes bicycle-type chains and gearing disposed to rotate a frame in response to human peddling.
U.S. Pat. No. 1,887,410 to Holt describes an amusement device which includes a platform rotated by rider peddling.
While human powered centrifuge devices are generally known, the prior art does not provide a controllable platform in which a specific G force can be maintained constant while power input varies. Furthermore, no device can provide both "passive" increased G exposure (no exercise) or "active" (with exercise) increased G exposure.